Issue 38

S. Tsutsumi et alii, Frattura ed Integrità Strutturale, 38 (2016) 244-250; DOI: 10.3221/IGF-ESIS.38.33 244 Focussed on Multiaxial Fatigue and Fracture Fatigue life assessment of a non-load carrying fillet joint considering the effects of a cyclic plasticity and weld bead shape S. Tsutsumi, K. Morita, R. Fincato, H. Momii Joining and Welding Research Institute, Osaka University, Japan tsutsumi@jwri.osaka-u.ac.jp , http://orcid.org/0000-0001-2345-6789 morita@jwri.osaka-u.ac.jp , http://orcid.org/0000-0002-2345-6790 fincato@jwri.osaka-u.ac.jp , http://orcid.org/0000-0002-2345-6791 hideto.momii@estech.co.jp http://orcid.org/0000-0003-2345-6792 A BSTRACT . Fatigue life depends strongly on irreversible contributions that accumulate during cyclic loading and unloading of structures. However, the correct identification of the loading path in terms of uniaxial or multi-axial stress states, proportional or non-proportional loading is essential because these factors can significantly alter the material response. In this study, finite element analysis was conducted to assess the fatigue crack initiation life of a non-load carrying fillet joint by considering weld bead shape and a cyclic plasticity accumulation during fatigue loading, which is a main cause of crack initiation. Cyclic plasticity behaviour including cyclic hardening and softening together was investigated with an unconventional plasticity model called the subloading surface model and extended to include both elastic boundary and cyclic damage concepts. The cyclic plasticity model can capture realistic plastic strain accumulation during high cycle fatigue under macroscopically elastic stressing conditions. K EYWORDS . Unconventional plasticity; Fatigue; Loading path; Crack initiation. Citation: Tsutsumi, S., Morita, K., Fincato, R., Momii, H., Fatigue life assessment of a non-load carrying fillet joint considering the effects of a cyclic plasticity and weld bead shape, Frattura ed Integrità Strutturale, 38 (2016) 244-250. Received: 30.06.2016 Accepted: 27.07.2016 Published: 01.10.2016 Copyright: © 2016 This is an open access article under the terms of the CC-BY 4.0, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. I NTRODUCTION s many welded structures such as bridges reach the age at which they are projected to require maintenance, techniques to calculate their fatigue life accurately and to prolong it, are needed [1]. In addition, it is also necessary to estimate the fatigue life of pre-existing structures because most structures are already damaged. Fatigue life is determined by irreversible deformations, which tend to accumulate during the life of components as a result of loading and unloading. The correct identification of the loading path is vital because different factors can alter the material response substantially [2-3]. Numerical modeling based on the finite element (FE) method has been used to predict weld-induced residual stresses [4]. Numerical techniques are an important part of most structural research because they can be used to analyze the behavior A